1. Field of the Invention
The present invention relates to a vacuum pump used in, for example, a semiconductor manufacturing apparatus, an electron microscope, a surface analysis apparatus, a mass spectrograph, a particle accelerator, and a nuclear fusion experiment apparatus.
2. Description of the Related Art
Semiconductor manufacturing involves processes, such as dry etching and CVD, and these processes are conducted in a vacuum vessel called a process chamber. A gaseous product generated during such a process (hereinafter referred to as xe2x80x9cproduct gasxe2x80x9d) is discharged to the exterior through a vacuum pump mounted to the vacuum vessel. Depending on a relationship between temperature and pressure inside the vacuum pump, some product gases can be solidified or liquefied inside the vacuum pump. In some cases, the solidified or liquefied product adheres to or is accumulated in the interior of the vacuum pump, preventing normal operation of the vacuum pump.
In the case of a vacuum pump used in processes such as dry etching and CVD, a band heater, for example, is conventionally attached to the outer periphery of the pump case of the vacuum pump in order to prevent adhesion and accumulation of the product, warming the vacuum heater by using this band heater.
However, in the case of a vacuum pump such as a turbo-molecular pump, in which gas is exhausted through rotation of a rotor, the rotor temperature cannot be made so high in view of a relationship among the specific strength, high-temperature creep, etc. of the materials for the rotor and the rotor blades integrally formed on the outer peripheral surface of the rotor. Thus, the temperature of the band heater has to be set relatively low, so that it is impossible to sufficiently prevent adhesion and accumulation of the product inside the vacuum pump.
The present invention has been made with a view toward solving the above problem. It is an object of the present invention to provide a vacuum pump capable of effectively preventing adhesion and accumulation of the product inside the pump while appropriately controlling the rotor temperature.
To achieve the above object, there is provided, in accordance with the present invention, a vacuum pump equipped with a pump mechanism portion for discharging gas from a vacuum vessel through rotation of a rotor installed in a pump case, a heater for warming the interior of the pump case, and a water-cooling tube for cooling the pump case, characterized in that it includes: a send-out means for sending out a parameter constituting a factor determining the temperature of the rotor; and a memory for storing the relationship between the parameter and the set temperature of the heater as a database, and characterized in that when the parameter sent out from the send-out means is input, the set temperature of the heater is determined from the database in the memory on the basis of the input parameter.
It is possible to adopt an arrangement in which the send-out means obtains and sends out as the parameter at least one of the following items of information consisting of pump ambient air temperature, the temperature and flow rate of pump cooling water, the kind and flow rate of pump evacuation gas, and pump exhaust pressure.